The present invention relates to particulate laundry detergent compositions containing anionic surfactants in the form of granules having a low to moderate bulk density and excellent dissolution properties. The compositions are especially suitable for use in low-temperature and/or low agitation wash processes, more particularly for washing by hand.
Laundry detergent powders containing high levels of anionic surfactants are widely known and used for washing fabrics by hand, the high levels being desirable in order to provide effective soil removal and good foaming. However, it has been found that poor powder properties can be encountered in high-active compositions, for example, powder stickiness leading to agglomeration and poor flow. The higher the desired surfactant content, the less space is available in the formulation for inorganic ingredients, for example builders, to provide porosity and to carry the organic surfactants.
Traditionally, built detergent powder contain a base powder, prepared by spray-drying or non-tower granulation or a combination of such processes, consisting of structured particles containing all, or the major part of, the surfactant and builder in the formulation. Other ingredients that are not suitable for incorporation into the base powder, for example, bleaches, enzymes and perfume, are subsequently admixed with the base powder.
In WO 98 54289A (Unilever) published on Dec. 3, 1998, it has been disclosed that higher total surfactant levels can be achieved without sacrificing powder properties if the traditional base powder is supplemented, or replaced altogether, by separate granular components in which certain ingredients are concentrated or segregated from one another. For example, the powder may be a xe2x80x9cmodularxe2x80x9d one composed of granules containing a high level of anionic surfactant, granules containing a high level of nonionic surfactant, and builder granules containing little or no surfactant.
The anionic surfactant granules disclosed contain from 60 to 99% by weight, preferably from 65 to 96% by weight, of anionic surfactant, for example, linear alkylbenzene sulphonate (LAS). These granules, which are also disclosed in WO 96 06916A, WO 96 06917A, WO 97 32002A and WO 97 32005A (Unilever), are preferably prepared by in-situ neutralisation of LAS acid by sodium carbonate in a flash dryer.
These granules may also be used in formulations which represent a compromise between the traditional and xe2x80x9cmodularxe2x80x9d approaches. WO 98 54287A (Unilever) published on Dec. 3, 1998 discloses laundry detergent powders which comprise a traditional phosphate-built base powder in combination with at least 10 wt % by weight of the high-anionic surfactant granules discussed above.
The anionic surfactant granules disclosed in the earlier filed Unilever patent applications discussed above are of high bulk density, so that they are less suitable for use in lower-bulk-density powders. For handwashing, however, lower-density, more porous products are generally preferred because they dissolve more quickly and completely, which is important when the wash is carried out under conditions of relatively low temperature and low agitation.
It has now been discovered that a similar, wholly or partially xe2x80x9cmodularxe2x80x9d approach may be adopted for powders of lower bulk density, using a different anionic surfactant (linear alkylbenzene sulphonate, LAS) granule having a lower bulk density and a somewhat lower surfactant loading, but still higher than can be obtained using a traditional base powder. This surfactant granule is prepared by a in-situ neutralisation process using a fluidised bed.
WO 94 07990A (Henkel) discloses anionic surfactant granules of high surfactant content prepared using a fluidised bed. The process may involve in-situ neutralisation, for example, primary alcohol sulphate (PAS) paste and a minor amount of LAS acid may be granulated with sodium carbonate on a fluidised bed.
Preparation of detergent base powders containing anionic surfactants (up to 31 wt %) by in-situ neutralisation on a fluidised bed is disclosed in WO 96 04359A (Unilever).
The present invention provides a particulate laundry detergent composition composed of at least two different granular components, comprising
(a) a granular anionic surfactant component having a bulk density within the range of from 300 to 600 g/l comprising:
(a1) from 40 to 55 wt % of linear alkylbenzene sulphonate (LAS),
(a2) from 45 to 60 wt % of a particulate carrier material comprising
(a21) from 30 to 100 wt % of sodium carbonate,
(a22) optionally from 0 to 70 wt % of finely-divided water-insoluble particulate material,
with the proviso that the carrier material must contain from 25 to 70 wt % of finely-divided water-insoluble particulate material (a22) if the average particle size of the sodium carbonate exceeds 40 xcexcm, the percentages being based on the carrier material;
(b) at least one other granular detergent component selected from
(b1) a detergent base powder composed of structured particles comprising anionic surfactant, builder, optionally nonionic surfactant and optionally other detergent ingredients,
(b2) a builder granule,
(b3) a granule containing at least 30 wt % of alkyl ether sulphate,
(b4) a granule containing at least 20 wt % of nonionic surfactant.
The invention also provides a process for the preparation of the anionic surfactant granule (a) defined above, which process comprises contacting alkylbenzene sulphonic acid with at least sufficient sodium carbonate to effect neutralisation of the alkylbenzene sulphonic acid, optionally together with a finely-divided water-insoluble particulate material, in a fluidised bed whereby neutralisation and granulation are effected, the amount of alkylbenzene sulphonic acid being sufficient to provide a content of alkylbenzene sulphonate in the granular detergent component obtained thereby of from 40 to 55 wt %.
A further subject of the invention is an anionic surfactant granule (a) as defined previously, prepared by the process defined in the previous paragraph.
The detergent composition of the invention is composed of at least two different granular components, one of which is a defined anionic surfactant (LAS) granule. The other may be a base powder, a builder granule, an alkyl ether sulphate granule, or a nonionic surfactant granule. Unless the other granular component is a base powder, the composition is xe2x80x9cmodularxe2x80x9d and preferably comprises at least three different components: for example, as well as the LAS granule, a builder granule and at least one other surfactant granule.
Whether or not xe2x80x9cmodularxe2x80x9d, the composition preferably Contains from 2 to 50 wt % of the LAS granule (a) and from 50 to 98 wt % of other granular components (b), the percentages being based on the total amount of the granular components (a) and (b).
The Anionic Surfactant (LAS) Granule (a)
In the LAS granule (a), the content of LAS ranges from 40 to 55 wt %, preferably from 40 to 50 wt %. The granule has a bulk density within the range of from 300 to 600 g/litre, the 400 to 500 g/litre range being especially preferred. Powder properties and dissolution properties are excellent.
The carrier material, present in an amount of from 45 to 60 wt %, is composed principally of sodium carbonate, but in some circumstances a finely divided water-insoluble particulate material is also present. It has been found that, in order to obtain the desired surfactant loading of at least 40 wt % in combination with good powder properties, it is necessary either to use a finely-divided water-insoluble particulate material to supplement the sodium carbonate, and/or use sodium carbonate that has been milled to a smaller than normal average particle size.
If the sodium carbonate has an average particle size not exceeding 40 xcexcm, then the presence of finely-divided water-insoluble particulate material is not necessary; but may in any case be desirable. Sodium carbonate milled to an average particle size within the range of 20 to 30 xcexcm may suitably be used. Micronised or micropulverised sodium carbonate (typical average particle size less than 5 xcexcm) may if desired be used but such a very small particle size is not essential. The particle size quoted here is the average weighted surface diameter or Sauter mean diameter d3,2.
If the sodium carbonate has an average particle size of 40 xcexcm or above, then the presence of finely-divided water-insoluble particulate material appears to be essential in order to achieve an anionic surfactant loading of 40 wt % or above. The finely-divided water-insoluble particulate material may be selected, for example, from zeolites, kaolin, calcite, silicas and silicates. The preferred material is zeolite.
The zeolite may be zeolite 4A or, preferably, zeolite MAP as described and claimed in EP 384 070B (Unilever) and commercially available as Doucil (Trade Mark) A24 from Crosfield Chemicals. Especially preferred is a carrier comprising sodium carbonate and zeolite in a weight ratio of from 70:30 to 30:70.
Preparation of the LAS Granule (a)
The LAS granule is prepared by in-situ neutralisation using a fluidised bed. The process comprises contacting an appropriate amount of LAS acid with at least sufficient sodium carbonate to effect neutralisation, optionally together with zeolite or other finely-divided water-insolunble particulate material, in a fluidised bed whereby neutralisation and granulation are effected.
In the process, the solids (sodium carbonate and, if present, zeolite or other finely-divided water-insoluble particulate material) are fluidised and the LAS acid is sprayed on at a suitable rate and with a suitable droplet size.
If desired, part of the carbonate, or part of the finely divided water-insoluble particulate material, if present, may be retained and dosed at the end of the process as layering material.
Other Granules (b)
As indicated previously, the compositions of the invention contain at least one other granule (b).
This may be a base powder, a product composed of structured particles containing both surfactant and builder, and optionally other minor ingredients suitable for incorporation into a base powder (for example, fluorescers, antiredeposition polymers such as sodium carboxymethyl cellulose). The base powder may be spray-dried, prepared by wholly non-tower granulation (also known as agglomeration), or prepared by any combination of these techniques (for example, spray-drying followed by densification).
In this case, where a base powder is present, the final composition may consist essentially of the base powder (b), the anionic surfactant granule (a), and any usual postdosed ingredients, for example, bleaches, enzymes, perfumes. Postdosed ingredients are discussed in more detail below under xe2x80x9cDetergent ingredientsxe2x80x9d.
However additional granules developed primarily for a xe2x80x9cmodularxe2x80x9d approach may also be present if desired. Between the extremes of the xe2x80x9ctraditionalxe2x80x9d powder in which the LAS granule is present essentially to boost the surfactant carrying capacity of the base powder, and the wholly xe2x80x9cmodularxe2x80x9d powder in which all surfactants and builders are present as separate granules, various intermediate formulations and combination granules can of course be envisaged.
Builder Granules
Builder granules may typically be based either on sodium tripolyphosphate or on zeolite, with various minor ingredients but only insignificant levels of, or no, surfactant. Builder granules may be prepared by spray-drying or non-tower routes or mixtures of the two. Builder compounds are discussed in more detail below under xe2x80x9cDetergent ingredientsxe2x80x9d.
Alkyl Ether Sulphate Granules
A preferred ingredient which can enrich the overall anionic surfactant content of the composition is an alkyl ether sulphate granule as described and claimed in our copending International patent application of even date claiming priority from British Patent Application No. 98 25558.1 filed on Nov. 20, 1998. This granule comprises at least 30 wt % of alkyl ether sulphate and a carrier material comprising a silica or silicate having a liquid carrying capacity of at least 1.0 ml/g.
Nonionic Surfactant Granules
one preferred nonionic surfactant granule comprises at least 55 wt % o f nonionic surfactant and a carrier material comprising a silica or silicate having a liquid carrying capacity of at least 1.0 ml/g. These granules are described and claimed in WO 98 54281A (Unilever) published on Dec. 3, 1998.
An alternative nonionic surfactant granule, which is especially preferred on account of its excellent dissolution properties, comprises from 20 to 30 wt % of nonionic surfactant and a non-spray-dried particulate carrier material comprising s odium carbonate together with sodium bicarbonate and/or sodium sesquicarbonate, and the sodium salt of a solid water-soluble organic acid. These granules are described and claimed in our copending International patent application of even date claiming priority from British Patent Application No. 98 25560.7 filed on Nov. 20, 1998.
Detergent Ingredients
The finished detergent composition, whether containing a base powder or a number of different granules, will contain detergent ingredients as follows.
As previously indicated, the detergent compositions will contain, as essential ingredients, one or more detergent active compounds (surfactants) which may be chosen from soap and non-soap anionic, cationic, nonionic, amphoteric and zwitterionic detergent active compounds, and mixtures thereof.
Many suitable detergent active compounds are available and are fully described in the literature, for example, in xe2x80x9cSurface-Active Agents and Detergentsxe2x80x9d, Volumes I and II, by Schwartz, Perry and Berch.
The preferred detergent active compounds that can be used are soaps and synthetic non-soap anionic and nonionic compounds.
Anionic surfactants are well-known to those skilled in the art. Examples include alkylbenzene sulphonates, particularly linear alkylbenzene sulphonates having an alkyl chain length of C8-C15; primary and secondary alkylsulphates, particularly C8-C15 primary alkyl sulphates; alkyl ether sulphates; olefin sulphonates; alkyl xylene sulphonates; dialkyl sulphosuccinates; and fatty acid ester sulphonates. Sodium salts are generally preferred.
Nonionic surfactants that may be used include the primary and secondary alcohol ethoxylates, especially the C8-C20 aliphatic alcohols ethoxylated with an average of from 1 to 20 moles of ethylene oxide per mole of alcohol, and more especially the C10-C15 primary and secondary aliphatic alcohols ethoxylated with an average of from 1 to 10 moles of ethylene oxide per mole of alcohol. Non-ethoxylated nonionic surfactants include alkylpolyglycosides, glycerol monoethers, and polyhydroxyamides (glucamide).
Cationic surfactants that may be used include quaternary ammonium salts of the general formula R1R2R3R4N+ Xxe2x88x92 wherein the R groups are long or short hydrocarbyl chains, typically alkyl, hydroxyalkyl or ethoxylated alkyl groups, and X is a solubilising cation (for example, compounds in which R1 is a C8-C22 alkyl group, preferably a C8-C10or C12-C14 alkyl group, R2 is a methyl group, and R3 and R4, which may be the same or different, are methyl or hydroxyethyl groups); and cationic esters (for example, choline esters).
Amphoteric surfactants, for example, amine oxides, and zwitterionic surfactants, for example, betaines, may also be present.
Preferably, the quantity of anionic surfactant is in the range of from 5 to 50% by weight of the total composition.
More preferably, the quantity of anionic surfactant is in the range of from 8 to 35% by weight.
Nonionic surfactant, if present, is preferably used in an amount within the range of from 1 to 20% by weight.
The total amount of surfactant present is preferably within the range of from 5 to 60 wt %.
The total amount of alkyl ether sulphate or other heat-sensitive surfactant present may suitably range from 1 to 20 wt %, preferably from 1.5 to 15 wt % and more preferably from 2 to 10 wt %.
The compositions may suitably contain from 10 to 80%, preferably from 15 to 70% by weight, of detergency builder. Preferably, the quantity of builder is in the range of from 15 to 50% by weight.
The detergent compositions may contain as builder a crystalline aluminosilicate, preferably an alkali metal aluminosilicate, more preferably a sodium aluminosilicate (zeolite).
The zeolite used as a builder may be the commercially available zeolite A (zeolite 4A) now widely used in laundry detergent powders. Alternatively, the zeolite may be maximum aluminium zeolite P (zeolite MAP) as described and claimed in EP 384 070B (Unilever), and commercially available as Doucil (Trade Mark) A24 from Crosfield Chemicals Ltd, UK. Zeolite MAP is defined as an alkali metal aluminosilicate of zeolite P type having a silicon to aluminium ratio not exceeding 1.33, preferably within the range of from 0.90 to 1.33, preferably within the range of from 0.90 to 1.20.
Especially preferred is zeolite MAP having a silicon to aluminium ratio not exceeding 1.07, more preferably about 1.00. The particle size of the zeolite is not critical. Zeolite A or zeolite MAP of any suitable particle size may be used.
Also preferred according to the present invention are phosphate builders, especially sodium tripolyphosphate. This may be used in combination with sodium orthophosphate, and/or sodium pyrophosphate.
Other inorganic builders that may be present additionally or alternatively include sodium carbonate, layered silicate, amorphous aluminosilicates.
Organic builders that may be present include polycarboxylate polymers such as polyacrylates and acrylic/maleic copolymers; polyaspartates; monomeric polycarboxylates such as citrates, gluconates, oxydisuccinates, glycerol mono-di-and trisuccinates, carboxymethyloxysuccinates, carboxy-methyloxymalonates, dipicolinates, hydroxyethyliminodiacetates, alkyl- and alkenylmalonates and succinates; and sulphonated fatty acid salts.
Organic builders may be used in minor amounts as supplements to inorganic builders such as phosphates and zeolites. Especially preferred supplementary organic builders are citrates, suitably used in amounts of from 5 to 30 wt %, preferably from 10 to 25 wt %; and acrylic polymers, more especially acrylic/maleic copolymers, suitably used in amounts of from 0.5 to 15 wt %, preferably from 1 to 10 wt %.
Builders, both inorganic and organic, are preferably present in alkali metal salt, especially sodium salt, form.
Builders are normally wholly or predominantly included in the granular components, either in the base powder or in a separate builder granule.
Detergent compositions according to the invention may also suitably contain a bleach system. It is preferred that the compositions of the invention contain peroxy bleach compounds capable of yielding hydrogen peroxide in aqueous solution, for example inorganic or organic peroxyacids, and inorganic persalts such as the alkali metal perborates, percarbonates, perphosphates, persilicates and persulphates. Bleach ingredients are generally post-dosed as powders.
The peroxy bleach compound, for example sodium percarbonate, is suitably present in an amount of from 5 to 35 wt %, preferably from 10 to 25 wt %. The peroxy bleach compound, for example sodium percarbonate, may be used in conjunction with a bleach activator (bleach precursor) to improve bleaching action at low wash temperatures. The bleach precursor is suitably present in an amount of from 1 to 8 wt %, preferably from 2 to 5 wt %.
Preferred bleach precursors are peroxycarboxylic acid precursors, more especially peracetic acid precursors and peroxybenzoic acid precursors; and peroxycarbonic acid precursors. An especially preferred bleach precursor suitable for use in the present invention is N, N, Nxe2x80x2, Nxe2x80x2-tetracetyl ethylenediamine (TAED).
A bleach stabiliser (heavy metal sequestrant) may also be present. Suitable bleach stabilisers include ethylenediamine tetraacetate (EDTA), ethylenediamine disuccinate (EDDS), and the aminopolyphosphonates such as ethylenediamine tetramethylene phosphonate (EDTMP) and diethylenetriamine pentamethylene phosphonate (DETPMP).
The detergent compositions may also contain one or more enzymes. Suitable enzymes include the proteases, amylases, cellulases, oxidases, peroxidases and lipases usable for incorporation in detergent compositions.
Preferred proteolytic enzymes (proteases) are catalytically active protein materials which degrade or alter protein types of stains when present as in fabric stains in a hydrolysis reaction. They may be of any suitable origin, such as vegetable, animal, bacterial or yeast origin.
Proteolytic enzymes or proteases of various qualities and origins and having activity in various pH ranges of from 4-12 are available. Proteases of both high and low isoelectric point are suitable.
Other enzymes that may suitably be present include lipases, amylases, and cellulases including high-activity cellulases such as xe2x80x9cCarezymexe2x80x9d).
Detergency enzymes are commonly employed in granular form in amounts of from about 0.1 to about 3.0 wt %. However, any suitable physical form of enzyme may be used.
Antiredeposition agents, for example cellulose esters and ethers, for example sodium carboxymethyl cellulose, may also be present.
The compositions may also contain soil release polymers, for example sulphonated and unsulphonated PET/POET polymers, both end-capped and non-end-capped, and polyethylene glycol/polyvinyl alcohol graft copolymers such as Sokalan (Trade Mark) HP22. Especially preferred soil release polymers are the sulphonated non-end-capped polyesters described and claimed in WO 95 32997A (Rhodia Chimie).
The compositions of the invention may also contain dye transfer inhibiting polymers, for example, polyvinyl pyrrolidone (PVP), vinyl pyrrolidone copolymers such as PVP/PVI, polyamine-N-oxides, PVP-NO etc.
The detergent composition may contain water-soluble alkali metal silicate, preferably sodium silicate having a SiO2:Na2O mole ratio within the range of from 1.6:1 to 4:1.
Other materials that may be present in detergent compositions of the invention include fluorescers; photobleaches; inorganic salts such as sodium sulphate; foam control agents or foam boosters as appropriate; dyes; coloured speckles; perfumes; and fabric conditioning compounds.
Ingredients which are normally but not exclusively postdosed, may include bleach ingredients, bleach precursor, bleach catalyst, bleach stabiliser, photobleaches, alkali metal carbonate, water-soluble crystalline or amorphous alkaline metal silicate, layered silicates, anti-redeposition agents, soil release polymers, dye transfer inhibitors, fluorescers, inorganic salts, foam control agents, foam boosters, proteolytic, lipolytic, amylitic and cellulytic enzymes, dyes, speckles, perfume, fabric conditioning compounds and mixtures thereof.